1. Field of the Invention
This invention relates generally to a television receiver using a synchronous video detector, and more particular to a television receiver having an automatic fine tuning system with a phase-locked loop.
2. Description of the Prior Art
A television receiver having an automatic fine tuning system with a phase-locked loop and a synchronous video detector is known from U.S. Pat. No. 3,946,148 (Skerlos).
A television receiver described in the above-mentioned U.S. Patent includes a variable frequency reference oscillator supplying a reference signal to a phase detector for an automatic fine tuning operation and to synchronous detector for a video detection.
An output signal of the phase detector is supplied to a local oscillator for a tuner through a first low pass filter and to the reference oscillator through a second low pass filter.
However, in the above-mentioned U.S. Patent, it is neccesary to insert an AC coupling between the phase detector and the second low pass filter whenever a phase-locked loop for the automatic fine tuning is formed.